•Shattered garnet grains observed in a Patagonian high pressure metasediment.•2D visco-elasto-plastic models used for assessing the mechanical conditions for fracturing.•Garnet in quartzite fractures ...under strain rates faster than for steady state creep rates.•Fractured garnet crystals in weak metasediments may record transient accelerated slip rates.
A paradox exists between the great number of intermediate-depth earthquakes occurring along active subduction interfaces worldwide and the extreme scarcity of paleo-seismic events recorded in exhumed metasediments from ancient subducted slabs. Recrystallization associated with exhumation-related overprinting generally contributes to the nearly-complete erasing of markers of unstable slip events in metamorphic rocks. We herein focus on a sample from an ancient deep thrust from a Cretaceous High-Pressure paleo-accretionary complex in Chilean Patagonia. A representative, moderately foliated micaschist exhibits broken garnet crystals that host a dense network of healed micro-fractures. While garnet fragments appear thoroughly disaggregated along the main foliation, the rock matrix that completely recrystallized has lost the record of brittle deformation. We employ a 2D visco-elasto-plastic numerical modelling approach in order to investigate the mechanical conditions that enable the fracturing of isolated garnet grains in a relatively weak matrix. The rupture of these stiff grains is achieved in our models at strain rates faster than 10−10 /s to 10−12 /s for elevated pore fluid pressures (80 to 99 % of the lithostatic value, respectively). Since high pore fluid pressures prevail in deep subduction interface settings, it is suggested that the rupture of these garnet crystals occurred through cataclastic deformation via (transient) slip rate acceleration, perhaps as a consequence of localized slip associated with slow to conventional earthquakes. Upon slip rate deceleration, viscous disaggregation of the broken garnet clasts occurred along with the erasing of the matrix cataclastic fabric.
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•Groundwater modelling in urban settings is complicated by altered recharge and infrastructure interactions with groundwater.•Scripted based model development, iterative ensemble smother (IES) ...methods, and cloud computing, can facilitate representation of the complexity of urban groundwater systems using extremely highly parameterized approaches.•This study presents an applied consulting project where new methods were used to better represent urban groundwater in numerical models.
Modelling of groundwater flow and transport in urban environments is complicated by changes in recharge due to urbanization, and interactions between groundwater, water supply networks and sewerage pipe infrastructure.
This study presents an applied groundwater modelling project that attempts to capture the complexity and quantify the uncertainty of groundwater flow and mass transport in urban environments using recently developed methods.
A python scripting approach was used for model development and preparation of a calibration constrained parameter uncertainty analysis using the iterative ensemble smoother method (IES). Water supply and sewer infrastructure locations were explicitly included in the numerical model as boundary conditions with adjustable parameters during the calibration. The model calibration, and predictive uncertainty analysis considered more than 100,000 independent parameters, which were applied at zones, pilot points and directly on the model grid to define model properties, boundary conditions, and initial conditions. Calibration observations included both water level and concentration measurements at 18 boreholes over the 12-year operational life of a remediation system. The IES method was applied to calibrate 120 alternative and equally plausible parameter realizations. Initial parameter values were produced from initial statistical distributions defined by parameter bounds and based on the conceptual hydrogeological model, literature review and spatial correlations of hydraulic properties observed in well tests. The Amazon EC2 cloud computing service was used to provide the parallel computing capacity necessary to complete the project within a reasonable timeframe.
Predictions of long-term mass transport towards a creek after the termination of active remediation were made with 47 of the resulting IES calibrated parameter sets. The IES method provided a distribution of potential impacts and allowed decisions about the future of the current remediation system to be made based on a quantitative, statistical, risk-based analysis. The extremely high degree of model parameterization allowed the complexity and uncertainty of an urban groundwater systems to be represented using adjustable model parameters, which reduced the likelihood of structural model error and biased predictions. This study found that fully python scripted model development and calibration setup, combined with IES, successfully allowed for improved representation of urban groundwater systems in numerical models. The post calibration groundwater flow budget of the model showed that groundwater interactions with sewer and water supply infrastructure are of similar magnitude to distributed recharge, and the omission of representing infrastructure in urban groundwater models could result in misleading predictions.
This paper provides a comprehensive review of metal additive manufacturing, a rapidly evolving field with innovative technologies and processes. The purpose of this review paper is to provide a ...complete picture of the current research on metal AM and its capabilities. An overview of metal AM and the current processing methods are provided, along with a brief introduction to the complex physics behind the melt pool formation. Common metal AM characteristic defects are discussed as well as the current metals and alloys that are commercially available. Furthermore, process optimization techniques and computational modelling methods are reviewed. Lastly, various post-processing methods to improve surface roughness, mechanical properties and dimensional precision are discussed. Although the library for printable alloys is increasing, there is still a need for alloy development outside of the commercial setting. Furthermore, there is currently not a complete numerical model of the AM process which is mainly due to the computational costs. Although metal AM is still in its infancy, the frequency and significance of new developments are driving AM to mainstream adoption.
In active earthquake zones, it is very likely that the structures would experience multiple shakings in major seismic events. For underground structures, the soil-structure interactions and the ...resultant dynamic responses could vary significantly according to the characteristics of the shakings. In this paper, the scenario of a shallow tunnel in liquefiable ground subject to multiple shakings is studied. The OpenSees platform and the PM4Sand constitutive model are employed to construct a plane-strain numerical model, where a rectangular tunnel is buried in saturated Hostun sand. Its validity is verified by the data from a centrifuge test of four consecutive shakings. The numerical soil-structure system is then configured for further investigation on the subject matter. Firstly, the liquefaction-induced uplift is identified as the main threat to the integrity of the tunnel in a seismic event of multiple shakings. Then, the pertinent soil-structure interactions are intensely discussed in a parametric analysis considering the influences of the permeability coefficient, the tunnel self-weight, and the shaking sequence.
•A centrifuge test on tunnel in liquefiable soil under multiple shakings is numerically modelled.•Liquefaction-induced uplift is identified as the main threat to the tunnel in such occasion.•The uplift under multiple shakings is intensely discussed in a parametric analysis.
Protonic ceramic electrolysis cells (PCECs) offer significant potential for large-scale green hydrogen production. The performance of conventional PCEC stacks is notably limited due to the uneven gas ...distribution. In this research, a new stack design using metal foam as the gas distributor is proposed and numerically evaluated using a 3D Multiphysics model to improve the gas distribution uniformity. At 1.3 V and 600 °C, the current density of the newly designed PCEC with metal foam is 173 % higher than that of the conventional PCEC. Moreover, the hydrogen production capability of metal foam based PCEC is 234 % higher than that of conventional PCEC, due to the improved gas distribution uniformity and faradaic efficiency (FE) of the new PCEC. The application of metal foam increases steam distribution uniformity by 91.2 %. In a conventional PCEC, the FE under the rib is notably lower than that under the channel. In contrast, the FE distribution is more uniform in a metal foam based PCEC. The improved performance in terms of current density, FE, and distribution uniformity highlights the potential of metal foam as a beneficial component in PCEC stacks. These findings contribute to the understanding and further development of PCEC technology.
•A 3D model is proposed for PCEC stack using metal foam for gas distribution.•Metal foam based PCEC stack outperforms the conventional PCEC stack.•Effects of operating and structural parameters on the PCECs are explored.•The impact of the flow field on faradaic efficiency is explored.
Wearable antennas can suffer from a variety of mechanical deformations that are induced by the body dynamic. The paper analyses how these complex deformations impact the performance of a flexible ...antenna operating in the 5-6 GHz band. The Green Coordinates spatial manipulation technique is used to generate a range of complex two-dimensional deformations, namely spherical, saddle, and twisting deformation. Generating full geometries is a key enabler in this study. The results offer valuable insight to the stability of antenna performance under in-situ deformations.
Numerical modeling and simulation approaches can be used to optimize material combinations, structural design, and process parameters to achieve the desired structural performance of 3D-printed ...structures. In this study, a novel CDW-based mortar mixture was prepared for the 3D concrete printing (3DCP) process. A square cross-sectional structure was designed and 3D-printed using a lab-scale gantry-type 3D printer for buildability analysis. The geopolymer material was also characterized to obtain time-dependent properties for use in a numerical model capable of predicting the buildability of concrete structures. In the numerical modeling and simulation phase, predictive simulations were performed for experimentally 3D-printed structures to validate the predictability of the numerical model. The numerical model revealed a sound approximation of buildability with an error of 6.3% only. Furthermore, using numerical simulations, sensitivity analyses were performed to evaluate the impact of designed height and 3DCP process parameters (i.e., printing speed and layer width) on the buildability of structures. The numerical modeling and simulation results revealed a strong impact of both process parameters (i.e., printing speed and layer width) on the buildability of 3D-printed structures. A maximum buildability of 410.6mm was achieved for structure 3D-printed at a printing speed of 20mm/s and layer width of 45mm. Overall, an improved buildability was observed for lower printing speeds and higher layer widths; however, the buildability performance was more sensitive to the layer width.
Hydrogen is pivotal in the transition to a sustainable energy supply. The presence of hydrogen-methane mixtures is increasing as the feasibility of utilizing existing natural gas infrastructure for ...large-scale hydrogen transportation and distribution. However, recent explosion accidents underscore the need to understand the detonation hazards of hydrogen and methane. Current modelling techniques for hydrogen-methane-air detonations are computationally prohibitive due to extra-fine mesh and time step requirements to solve the chemical reaction coupling within detonation structure. This study presented a generic approach to address these challenges, enabling precise and rapid simulation of hydrogen-methane-air blast profiles within hydrocodes. Modified open-source codes helped bypass the time-consuming implicit coupling of detailed chemical reactions with detonation structure and thermodynamic properties based on Chapman-Jouguet (C-J) theory and equilibrium reactive flow assumption, yielding a 90% reduction in computational time. An empirical model, developed through theoretic calculations, provided C-J parameters for hydrocode input with high accuracy across typical industrial conditions. Then, these C-J parameters were employed in LS-DYNA hydrocode based on modified Jones-Wilkins-Lee (JWL) equation of state (EoS) to simulate the hydrogen-methane-air blast loading. This approach was validated against diverse experimental data, encompassing hydrogen-air, methane-air, and hydrogen-methane-air mixtures, and various fuel concentrations, experimental scales, confinement conditions, and fuel shapes. Although conservative results were observed in unstable detonations near the lower detonable limit, it outperformed traditional CFD methods in both accuracy and efficiency. Furthermore, the use of hydrocodes enables the analysis of blast loading as well as the dynamic behaviour of structures subjected to explosive forces. This approach is easily adaptable to other gaseous detonations beyond hydrogen-methane-air by simply replacing the chemical reaction models, making it a versatile tool across various fields.
This paper focuses on the influence of the step drill bit geometry on the damage induced during drilling Carbon Fiber Reinforced Polymer materials (CFRPs). Step geometry designed with the aim of ...avoiding composite damage in CFRPs drilling, is compared to conventional twist configuration. Despite the reduction of thrust force and torque observed when using the step drill, the delamination was only reduced at low feed rates. A numerical model developed for the step geometry was validated with experimental data demonstrating its ability to predict thrust force and delamination for different values of feed rate and cutting speed. Numerical model allowed the development of a parametrical study. Finally, using a response surface methodology a mechanistic model and surface diagrams have been presented in order to help in the selection of optimum variables minimizing drilling induced damage.
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